This invention relates to a method for the detection of reciprocating machine (engine, compressor, etc.) faults and failures using the so-called Instantaneous Rotational Velocity (IRV) method.
Instantaneous Rotational Velocity (IRV) is based on the premise that the speed of an engine varies during each revolution. In the simplest case, a single cylinder engine, the gas in the cylinder is compressed by the rising piston and when the ignition of the gas occurs the piston is pushed back down. As the piston again rises, it is slowed down because of the energy required to compress the gas in the cylinder and by friction and inertial forces within the mechanical system. During the expansion stroke the piston is accelerated downward. This cyclical acceleration and deceleration is used to monitor the amount of energy (torque) that the piston supplies to the engine.
In a multi-cylinder engine each piston, in turn, provides energy to the system. Because cylinders fire in sequence there are a number of accelerations and decelerations every time that the engine completes a full revolution. By analyzing these speed variations it is possible to detect changes in the performance of the engine.
Considerable work has been done in the field of engine fault detection and analysis using engine speed fluctuations, as disclosed in the following articles:
Citron, S. J., O'Higgins, J. E. and Chen, L. Y., "Cylinder by cylinder engine pressure and pressure torque waveform determination utilizing speed fluctuations", SAE International Congress and Exposition, Detroit, Mich., Feb. 27-Mar. 3, 1989, Paper No. 890486.
Freestone, J. W. and Jenkins, E. G., "The diagnosis of cylinder power faults in diesel engines by flywheel speed measurement", International Conference on Vehicle Condition Monitoring, IMechE, London, England, 1985, Paper No. C33/85.
Mauer, G. F. and Watts, R. J., "On-line cylinder diagnostics on combustion engines by noncontact torque and speed measurements", SAE International Congress and Exposition, Detroit, Mich., Feb. 27-Mar. 3, 1984, Paper No. 890485.
Sood, A. K., Fahs, A. A. and Henein, N. A., "A real-time microprocessor-based system for engine deficiency analysis", IEEE Transaction on Industrial Electronics, Volume IE-30, Number 2, May 1983, p. 159.
Sood, A. K., Friedlander, C. B. And Fahs, A. A., "Engine fault analysis: part I--statistical methods", IEEE Transaction on Industrial Electronics, Volume IE-32, Number 4, November 1985, p. 294.
Sood, A. K., Fahs, A. A., and Henein, N. A., "Engine fault analysis: part II--parameter estimation approach", IEEE Transaction on Industrial Electronics, Volume IE-32, Number 4, November 1985, p. 301.
Likewise, several approaches have been patented to apply this technology towards diesel and spark ignition engines (see U.S. Pat. Nos. 4,843,870; 4,697,561; 4,532,592; 4,197,767; 4,292,670; 3,789,816).
The above prior art has been geared at using the variation of angular velocity as a fuel injection monitoring system and for the control of engines. It is the object of the present invention to use the angular velocity data to identify any changes in the condition of the engine.